The present invention relates to a pneumatic displacement system.
Pneumatic drive systems, currently called xe2x80x9cartificial musclesxe2x80x9d, are known, which are formed of inflatable tubes inserted in protection braids, such that the artificial muscle contracts or expands according to whether its internal fluid pressure increases or decreases. Such artificial muscles are, for example, described by B. Tondu and P. Lopez in xe2x80x9cCompte rendu de l""Acadxc3xa9mie des Sciencesxe2x80x9d, t. 320, pp. 105-114, 1995. In particular, such xe2x80x9cmusclesxe2x80x9d have been designed, which can have a length on the order of some ten centimeters and a diameter on the order of from 1 to 3 cm and which provide a contraction of the order of from 10 to 20% of their length when their internal pressure varies from the atmospheric pressure to a pressure which is 4 to 5 times greater. Such systems have the advantage of exhibiting an excellent power-to-weight ratio. For example, an artificial muscle having a weight on the order of from 50 to 100 grams can exert a force on the order of 1,000 newtons, that is, for example, lift a load on the order of 100 kg. Such drive systems are well adapted to an operation in hospital surroundings since they are clean, non polluting, and lend themselves to disinfection/sterilization operations. Further, they only use low-power and low-voltage electricity sources to control electrovalves. Further, compressed air sources are currently available in hospitals.
However, such systems have a disadvantage linked to their small movement which, as indicated, is on the order of 10 to 20% only between their idle position and their active position.
The present invention aims at providing a pneumatic displacement system exhibiting the same lightness, reliability, and security advantages as the above-mentioned artificial muscles, but further having a wide movement.
To achieve this object, the present invention provides a system of pneumatic displacement of a cable stretched in a loop between at least two pulleys, including at least one xe2x80x9cartificial musclexe2x80x9d inserted on a portion of the loop, the length of this artificial muscle varying according to whether it is or not under pressure, a means 20 for putting or not the artificial muscle under pressure, and means for alternately blocking two of said pulleys in at least one rotation direction.
According to an embodiment of the present invention, the system includes a single artificial muscle arranged on a branch of the loop and a resilient cable.
According to an embodiment of the present invention, the system includes several artificial muscles in series arranged on the same branch of the loop. FIG. 5 illustrates an example of a pneumatic displacement system comprising two artificial muscles in series arranged on the same branch of the loop.
According to an embodiment of the present invention, the system includes at least two artificial muscles respectively located on either side of a pulley, and means for putting under pressure in a complementary manner said artificial muscles at the rate at which the pulleys are blocked and unblocked. The cable is resilient.
According to an embodiment of the present invention, a device to be moved is directly linked to the cable as illustrated in FIG. 3.
According to an embodiment of the present invention, a device to be moved is linked to the cable via a pulley transmission system.
According to an embodiment of the present invention, at least one of the pulleys is linked to a fixed point via a resilient means.